The goals of this proposal are to develop non-replicating, rapidly acting mucosal vaccines capable of eliciting effective cross-protection against both Burkholderia mallei (Bm) and 6. pseudomallei (Bpm) pneumonic infection. This project will utilize cationic liposome-nucleic acid complex (CLDC) adjuvants for mucosal immunization (intranasal and oral administration) with Burkholderia antigens. The antigens to be evaluated include 7 Bm antigens, all of which have been shown to elicit at least partial protection in published or preliminary studies. We will test the hypothesis that effective cross-protection against inhaled B. mallei and B pseudomallei infection can be achieved bv mucosal administration of liposome-nucleic acid adiuvanted vaccines containing one to two immunogenic Burkholderia antigens. To test this hypothesis, we will undertake the following 4 specific aims. In Aim 1. the ability of Bm antigens to elicit cross-protection against both Bm and Bpm infection will be assessed. Mice will be immunized with CLDC-based vaccines containing recombinant Bm antigens and subjected to inhalational challenge with Bm and 6pm. In Aim 2. the CLDC adjuvant platform will be optimized for efficient mucosal immunization and the two most effective antigens from Aim 1 will be assessed for their ability to elicit protection in high-dose Bm and Bpm challenge studies following oral and intranasal immunization. The immunological mechanisms responsible for vaccine-induced protection, including humoral and cellular effector mechanisms, will be assessed in Aim 3. Finally, in Aim 4 we will determine whether combining mucosal vaccination with conventional antimicrobial therapy can generate improved protection from acute infection and prevent the establishment of chronic Burkholderia infection. This research project fits within the RMRCE Integrated Research Focus on Immunomodulation, Adjuvants and Vaccines, and will interact directly with RP 1.4 (Francisella immunoproteome) and RP 1.2 (Development of innate adjuvants) and will utilize the resources of Animal Models and Human Lung Cell Cores. RCRME objectives. Studies of Burkholderia immunity and development of new vaccines and adjuvants are priorities for the RMRCE program. The studies proposed here will identify new Burkholderia vaccine antigens and advance development of a broadly effective mucosal vaccine adjuvant suitable for protection of civilian and military populations from aerosolized Burkholderia infection. The vaccine adjuvant platform being developed here is also applicable to immunization against a number of other bacterial and viral pathogens.